Basque-style sidras are known for being acetic, complex and tart. I have achieved this flavor profile by inoculating a blend of fifty varieties of heirloom apples with the yeast from a half-dozen bottles of Basque cider. The fermentation occurred in an open-top tank to allow the natural flora of Portland to blend with the foreign yeasts. To add to the complexity and unpredictability, I added over a hundred pounds of local wild blackberries during the initial fermentation. The result is a vinegary, tart and full-bodied, fully-dry cider. Available in extremely limited quantities.